Stator or rotor of an electrical machine having basic and special bar conductors with multiple pitches

ABSTRACT

The present technology contemplates a stator or rotor of an electric machine comprising a main cylindrical body with a circular array of slots; at least one bar winding comprising a first and second plurality of basic conductors and a second plurality of special conductors. The first and second circular array comprise a first and second arc of legs of the first and second set of said conductors which are inserted as well as legs of the conductors. The present technology also contemplates electric machines and electric or hybrid drive vehicles comprising such stators of rotors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application that claims the benefit ofU.S. patent application Ser. No. 13/387,728, filed on Jan. 28, 2012,entitled “Method and Apparatus for Twisting Bar Conductors, inParticular for Bar Windings of Electric Machines”, which is a NationalStage Application of PCT/IT2010/000305, filed Jul. 8, 2010, entitled“Method and Apparatus for Twisting Bar Conductors, in Particular for BarWindings of Electric Machines”.

BACKGROUND

The present disclosure regards a stator or rotor of an electoral machineand also regards a method for twisting bar conductors, in particular forbar windings of electrical machines, and the related twisting apparatus.

Components of electrical machines are known, such as stators and rotors,which comprise bar conductors that are bent and connected together indifferent ways so as to make so-called bar windings.

In particular, belonging to the state of the art are bar windings madeby means of bar conductors having a essentially rectangular crosssection, where by rectangular it is intended both the square section andthe “flat” section with which a section of rectangular shape isgenerally indicated. In such “flat” section, one of the two sides haslower size with respect to the other.

The aforesaid bar conductors are usually preformed by means of‘U’-shaped or ‘P’-shaped bends, starting from straight bar conductors.The U.S. Pat. No. 7,480,987 describes a preforming method embodiment ofbar conductors (in such document termed “hairpin conductors”). Thepreforming is such to modify the form of the straight conductors in amanner such that they can be suitably inserted in suitable radiallyaligned pockets made in a twisting device adapted to deform, after theinsertion, the aforesaid preformed conductors. In practice, the twistingdevice essentially serves for “spreading” the legs of “U”-shaped or“P”-shaped form in order to ensure that two legs of a same conductor,after having extracted the latter from the twisting device, can besubsequently inserted in the slots of a stator or rotor core, radiallyoffset from each other by a predefined pitch.

The United States patent application published with number US2009/0178270 describes a method for twisting, with uniform pitch,preformed bar conductors after the insertion of the latter in thepockets of the twisting device.

The aforesaid twisting method makes the following steps:

the bending operation of the free end portions of the bar conductors(also called twisting from the welding side), after the insertion ofsuch conductors in the slots of a stator core, and

the subsequent operation of welding together such bent, free endportions.

There is therefore the need to provide a stator or rotor that can beproduced with an alternative twisting method to that described above,which simplifies the aforesaid operations of bending and welding of thefree end portions of the bar conductors.

DETAILED DESCRIPTION

The above need is satisfied with a stator or rotor as defined in generalin claim 1 and in the claims dependent thereon in particularembodiments.

Further characteristics and advantages of the present invention will bemore comprehensible from the description reported hereinbelow ofpreferred and non-limiting embodiments thereof, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a side view of a stator embodiment for anelectric machine, comprising a stator core and a bar stator winding;

FIG. 2 shows a perspective view of a first basic conductor type;

FIG. 3 shows a perspective view of a second basic conductor type;

FIG. 4 shows a perspective view of a bar conductor adapted to performthe function of phase terminal;

FIG. 5 shows a perspective view of a bar conductor adapted to performthe function of jumper;

FIG. 6 shows a perspective view of a bar conductor adapted to performthe function of a neutral conductor or star center;

FIG. 7 schematically shows a top view of a portion of the stator core,in which two slots are visible which are intended to be filled withpreformed insulating sheets and bar conductors;

FIG. 8 schematically shows a top view of a portion of the stator core,in which two slots filled with insulating sheets and bar conductors arevisible;

FIG. 9 represents a “P”-shaped preformed bar conductor;

FIG. 10 shows a top view of a twisting apparatus;

FIG. 11 shows a perspective view of a twisting device comprised in thetwisting apparatus of FIG. 10;

FIG. 12 shows a top view of the twisting device of FIG. 11 with someparts removed;

FIG. 13 shows an enlarged detail of FIG. 12;

FIG. 14 shows a further top view of the twisting device of FIG. 11;

FIG. 15 shows a further top view of the twisting device of FIG. 11;

FIG. 16 shows a further top view of the twisting device of FIG. 11;

FIG. 17 shows a further top view if the twisting device of FIG. 11;

FIG. 18 shows a further top view of the twisting device of FIG. 11;

FIG. 19 shows an exemplifying diagram of a possible type of conductorloading in the twisting device of FIG. 11; and

FIG. 20 shows a flow chart of a twisting method.

DETAILED DESCRIPTION

In the figures, equivalent or similar elements are indicated with thesame reference numbers.

For the purposes of the present description, by “flat” or “square” barconductor it is intended a bar conductor having four substantially flatsides, each joined to adjacent sides, typically by a rounded corner.

Therefore, the words “flat” or “square” or equivalent words used fordescribing the cross section of a bar conductor are used in a generalsense and must not be interpreted to exclude the fact that such barconductors have significantly rounded corners which join thesubstantially flat sides. The expression “flat conductor” should beintended in the sense that the conductor has two opposite sides whosedistance is greater than the distance between the remaining two oppositesides. For the purposes of the present invention, the expression“rectangular conductor” should be intended as a generalization of a flatconductor and square conductor, the square being a special rectangularconductor case in which the four sides have the same size.

With reference to the attached figures, with 1a stator is indicated inits entirety comprising a stator core 2. For example, the stator 1 isthe stator of an electric motor, e.g. for an electric or hybrid drivevehicle.

It is clear that such stator can also be used in an electric machineemployed as a generator or used for alternately performing motorfunction and generator function. In the enclosed figures, only thestator of such electric machine was represented, since it is deemed thatthe remaining parts of an electric machine or generally of an electricor hybrid drive vehicle are widely known to a man skilled in the art.

For the sake of simplicity and economy of description, a rotor will notbe described in detail in this venue since it is deemed that a manskilled in the art, to whom rotor structure is well known, will be ableto easily apply the teachings of the present description to a rotor.

In a per se known manner, the stator core 2 comprises a main, laminatedtubular body, for example made of magnetic material, which is axiallyextended (Z-Z axis) between two opposite faces 3,4, respectively knownas the insertion face 3 and the welding face 4.

The main body of the stator core 2 comprises a plurality of slots 8which are axially extended in the thickness of the main body and whichare crossed by bar conductors, S1, S2, S3 which overall form at leastone stator bar winding. In accordance with one embodiment, the barconductors U1, U2, S1, S2, S3 are covered on their surface by aninsulation layer of electrically insulating material, such as aninsulating enamel.

In accordance with one embodiment, the aforesaid bar conductors U1, U2,S1, S2, S3 are made of copper and are flat rectangular conductors, sincethey have a pair of opposite faces which are further away from eachother than the distance between the two remaining opposite faces.

In accordance with one embodiment, the bar conductors U1, U2, S1, S2, S3comprise a first plurality of basic conductors U1, U2 (also called“hairpin conductors”), and a second plurality of special conductorsS1-S3 which for example comprise terminals S1, jumpers S2 or the neutralconductor S3. As is known, the latter bar conductors S1-S3 representso-called special elements for the completion of the winding. In thepresent description, the expression “basic conductors” is exclusivelyused for identifying conductors that are not special elements of theabovementioned type, i.e. that are not specifically provided for thefunctional completion of the winding.

The basic bar conductors U1, U2 of the first plurality have a bentportion 15, or connection portion, which projects from the insertionface 3 of the stator core 2 and two legs 5 whose free end portions 7project from the other face 4 of the stator core 2, i.e. from thewelding face 4. The bent portion 15 is also often called “head portion”in the field. Among these basic conductors, there is a first conductortype U1 and a second conductor type U2 which mainly differ from eachother for the distance between the legs 5. As is known to a man skilledin the art, this difference also involves a certain difference in theoverall conductor length.

The basic bar conductors U1, U2 are obtained by spreading the legs 5 ofa preformed “U”—or “P”-shaped bar conductor 25 as is shown for examplein FIG. 9, by a pre-established amount or pitch. From hereon, for thesake of description simplicity and without introducing any limitation,the U- or P-shaped preformed bar conductors will be generally indicatedas “U-shaped preformed conductors”, intended the U as an approximationof the P of FIG. 9.

The spreading operation of the legs of the U-shaped preformed conductorsis generally known as twisting, and more precisely as twisting of the“head portions”, and the pre-established amount or pitch is known as“twisting pitch”. The latter is measured in number of slots 8. Forexample, the basic bar conductors of the first type U1 are obtained viatwisting of the U-shaped preformed conductor of type equivalent orsimilar to that represented in FIG. 9 according to a twisting pitchequal to nine slots, while the basic bar conductors of the second typeU2 are obtained via twisting of the “U”-shaped preformed conductor oftype equal or similar to that represented in FIG. 9 according to atwisting pitch equal to eight slots. It is clear that the aforesaidtwisting operation for the spreading of the legs 5 of a same “U”-shapedpreformed conductor requires—after having inserted said preformedconductors 25 subjected to twisting in the stator core—the next step ofbending the end portions 7 in order to allow the welding of suchportions necessary for making the winding. It is also clear that inorder to ensure that the basic conductors U1, U2 have, after thetwisting, connection portions 15 arranged at a same elevation, saidbasic conductors must be obtained from “U”-shaped preformed conductorsof different length.

Also the special conductors S1-S3 comprise at least one leg 5, one bentend portion 7 projecting from the welding face 4 and opposite,variously-shaped end portions 16, 17, 18 projecting from the insertionface 3.

With reference to FIGS. 7 and 8, each slot 8 of the stator core 2 iscrossed by at least two of the aforesaid bar conductors U1, U2, S1, S2,S3, and in particular by the legs 5 thereof, and houses a sheet 10, orcase 10, made of insulating material.

In accordance with a non-limiting embodiment, as shown in FIG. 3, in thecase in which the bar conductors are flat, the two bar conductors insidea same slot are aligned along a respective short side thereof.

It is observed that in the particular represented embodiment, each slot8 has a first and a second insertion position P1, P2 radially alignedwith respect to each other. When the legs 5 of the bar conductors U1,U2, S1, S2, S3 are inserted inside the slots 8, two circular andconcentric arrays S1, S2 of legs 5 are therefore defined in the stator1. Clearly, in the case in which each slot 8 has four insertionpositions, four circular and concentric arrays of legs 5 will bedefined, and so forth.

In FIG. 10, a twisting apparatus embodiment 30 is shown, comprising arotating table 36 adapted to move a twisting device 50 between differentwork stations 31-33, and particularly between a loading station 31 ofbasic preformed conductors, a subsequent loading station 32 of thespecial conductors 32, and a twisting station 33 and an extractionstation 34.

In FIGS. 11, 12, 13, a twisting device embodiment 50 is represented. Thetwisting device 50 comprises at least a first 51 and a second body 52coaxial with each other and extended around a twisting axis Zt-Zt,respectively comprising a first A1 and a second A2 circular array ofpockets centered around such axis Zt-Zt. In the particular indicatedembodiment, without introducing any limitation, each circular array A1,A2 comprises 72 pockets. It must be observed that in the case in whichthe slots of the stator have more than two insertion positions P1, P2,the twisting device 50 will comprise more than two pocket arrays.

The first and the second body 51, 52 are rotatable around the twistingaxis Zt-Zt in order to assume at least one insertion configuration, orconductor loading configuration, in which respective pockets of thefirst and the second circular array A1, A2 are radially aligned witheach other. By radial direction, it is intended a directionperpendicular to, and passing through, the twisting axis Zt-Zt. In theaforesaid insertion configuration, one or more U-shaped preformedconductors 25 can be inserted in a manner such that two legs 5 of theaforesaid U-shaped preformed conductors are inserted in a pair ofadjacent pockets, respectively radially aligned of the first A1 and thesecond A2 circular array. An operative loading configuration of thetwisting device 50 is for example represented in FIG. 12, in which withP_I a possible fixed loading position has been indicated.

The loading of the U-shaped preformed conductors 25 inside the twistingdevice 50 can, for example and without introducing any limitation, beattained in the loading station 31 by employing (for example) aninsertion device as described in the U.S. Pat. No. 7,721,413, which ishereby incorporated by reference. The U-shaped preformed conductors 25are, for example and without introducing any limitation, made by meansof an apparatus and a method as described in the U.S. Pat. No.7,480,987, which is hereby incorporated by reference. Possible variantsof the aforesaid apparatus are described in the patent publication Nos.WO2011/128919 and WO2011/135596, which are hereby incorporated byreference. Finally, in accordance with one non-limiting embodiment, thepockets of the twisting device 50 are made in accordance with theteachings of the patent publication No. WO2011/199207, which is herebyincorporated by reference.

In accordance with one embodiment, the twisting device 50 comprisesfirst locking elements 55 adapted to removably lock a relative rotationbetween the first 51 and the second 52 body and to allow, when activated(in other words, in a locking configuration), an integral rotation ofthe first 51 and the second 52 body with respect to an externalreference and around the twisting axis Zt-Zt. In accordance with oneembodiment, the aforesaid first locking elements comprise at least onespring clamp 55. For example, such spring clamp 55 is mainly housed in aseat made in one of said bodies 51, 52, in the embodiment in the body51, and comprises a helical spring 56 and a locking body 57, which inthe embodiment is represented by a sphere, which projects from such seatin order to be engaged in a locking seat c1, c2 provided in the other ofsaid bodies 51, 52, in the embodiment in the second body 52. Preferably,each spring clamp 55 is associated with two adjacent locking seats c1,c2. In the embodiment represented in FIG. 13, the centers of suchadjacent locking seats c1, c2 are angularly spaced from each other by5°, i.e. by the angular distance between the centers of two adjacentpockets. It is observed that in the particular embodiment represented,the first locking elements 55 are automatic and normally activated.

With reference to FIG. 11, in accordance with one embodiment, thetwisting device 50 comprises a plurality of the aforesaid first lockingelements 55.

In accordance with one embodiment, the twisting device 50 comprisessecond locking elements 61, 62 adapted to lock, in an independent mannerwith respect to each other, the first 51 and/or the second body 52 withan external reference, e.g. the rotating table 36, in order to prevent arotation of the bodies 51, 52 with respect to such reference. In theparticular represented embodiment, the second locking elements 61, 62comprise a first 61′ and a second 62′ punch, activatable/deactivatablein an independent manner with respect to each other by a respectivecontrol signal, in order to respectively assume an advanced position (asis represented, for example, in FIG. 12) and a moved-back position (asis for example represented in FIG. 14). For example, the aforesaidpunches 61′, 62′ are commanded by, or are part of, pneumatic cylinders.

In the advanced position or locking position, the punches 61′, 62′ areadapted to be selectively engaged in a respective plurality of lockingseats 91 a, 91 b, 91 c and 92 a, 92 b, 92 c, 92 d provided for on anexternal wall 71, 72 respectively of the first 51 and second 52 body.The second locking elements 61, 62 are for example integral with therotating table 36, so that it is understood that in the locking position(FIG. 12) the punches 61′, 62′ can lock the bodies 51, 52 to therotating table 36, therefore preventing a rotation of said bodies 51, 52with respect to an external reference. With reference to FIG. 14, it isobserved that on the contrary, in the moved-back position or unlockedposition, the punches 61′, 62′ do not prevent a rotation of the twobodies 51, 52 with respect to an external reference. In accordance withone embodiment, at least one of the aforesaid locking seats 91 a, 91 b,91 c and 92 a, 92 b, 92 c is a seat with clearances, adapted to allow arotation of the associated body 51, 52 for a predefined and limitedangular travel with respect to an external reference, even when therespective punch 61′, 62′ is in advanced position. In the particularrepresented embodiment, two such locking seats with clearances 91 c and92 d are provided for, associated with the first and the second body 51,52, respectively.

In accordance with one embodiment, the second locking elements 61, 62are adapted to lock one of the aforesaid bodies 51, 52 to a fixedreference in a manner such that, by driving in rotation the other ofsaid bodies, such bodies can carry out a relative rotation with respectto each other, overcoming the opposing resistance of the first lockingmeans 55. In other words, the second locking means 61, 62 prevail withrespect the first locking elements 55.

Described below is an example of operation of a twisting apparatus anddevice, as described above.

In FIG. 12, the twisting device 50 is represented in an operativeinsertion configuration. In such configuration, the twisting device 50is positioned at the loading station 31. In such station 31, a stepperservo motor, or generally a rotational stepper drive device not shown inthe figures, is coupled to the first body 51. In the aforesaid insertionconfiguration, the two bodies 51, 52 are locked to the rotating table36, the two punches 61′ and 62′ being in the advanced position andengaged in respective locking seats 91 a, 92 a. In this configuration,in which each pocket of the first body 51 is radially aligned with arespective pocket of the second body 52, the first U-shaped preformedconductor 25 is inserted, i.e. loaded, in the twisting device 50, inparticular in the two radially aligned pockets arranged at the fixedinsertion position P_I. Subsequently, the two punches 61′, 62′ arebrought into the moved-back position and by means of the servo motor thefirst body 51 is rotated around the twisting axis Zt-Zt, in thedirection of the arrow Fr (i.e. in clockwise sense in the figures). Thesecond body 52 is also driven in rotation, since it is locked to thefirst body 51 by means of the clamps 55. In the represented embodiment,the rotation carried out has an amplitude of 5°. After such rotation,the twisting device 50 reaches the further insertion configuration ofFIG. 14, in which for the sake of simplicity, the U-shaped preformedconductor 25 inserted in the pockets indicated by the arrow F1 is notrepresented. With the punches 61′, 62′ in moved-back position, oneproceeds pitch after pitch in the above-described manner untilfifty-four of the seventy-two slots are filled, therefore reaching theconfiguration of FIG. 15 in which the punches 61′, 62′ are brought intoadvanced position and are engaged in the locking seats with clearances91 c and 92 d. In such configuration, all of the pockets starting fromthe arrow F54 going in clockwise sense up to the arrow F1 were thereforeloaded with respective U-shaped preformed conductors 25. It is hencepossible in such position to identify a subset of pockets occupied by arespective leg 5 of a U-shaped preformed conductor 25 and a residualsubset of free pockets. In the particular embodiment described up tonow, the subset of occupied pockets and the subset of free pockets formtwo circumference arcs complementary to each other.

At this point, in accordance with one embodiment, the first body 51 isdriven in rotation for two consecutive pitches: the first is providedfor bringing two free, radially aligned pockets to the insertionposition P_I, while the second is provided for making a twist, and inparticular a spread, of the U-shaped preformed conductors 25 inserted inthe twisting device 50. In particular, in the embodiment represented atthe first pitch, both bodies 51, 52 rotate by 5°, while due to the widthdifferences of the seats with clearances 91 c, 92 d, at the second pitchonly the first body 51 rotates, since the second body 52 is locked bythe associated punch 62′. By means of the aforesaid relative rotation ofone pitch between the two bodies 51, 52, the further insertionconfiguration of FIG. 16 is attained in which all the U-shaped preformedconductors 25 loaded in the twisting device 50 have undergone a twistingof 5°; in the represented embodiment, this corresponds to the angulardistance between the centers of two adjacent pockets. With reference toFIGS. 13 and 16, it is observed that the relative rotation between thetwo bodies 51, 52 determines the passage of the sphere 57 from thelocking seat c1 to the locking seat c2. Starting from the configurationof FIG. 16, the two punches 61′, 62′ are brought into moved-backposition and—driving in rotation the first body 51 and thus the secondbody 52 at every pitch—the subset of free pockets are loaded with aplurality of U-shaped preformed conductors 25, leaving the pocketsintended to receive the special conductors S1, S2, S3 free.

One possible exemplifying pattern for the filling of the pockets of thetwisting device 50 is represented in FIG. 19. As can be appreciated, theexternal pockets are loaded with legs 5 which form a first continuouscircumference arc (from the arrow F5 to the arrow F6 in clockwisedirection). Also the inner pockets are loaded with legs 5 which form asecond continuous circumference arc (from the arrow F7 to the arrow F8in clockwise direction). All the pockets of the first and second archouse legs 5 of U-shaped preformed conductors 25 which in the embodimentwere subjected to a twisting of 5°, or more generally to a twisting of afirst predefined pitch. Such first pitch is not constrained to be equalto the angular distance between the centers of two adjacent pockets, butrepresents a design parameter.

The pockets marked by a square are instead intended to receive legs ofspecial conductors S1, S2, S3 and are left free. The remaining pockets,marked by a circle, house legs 5 of U-shaped preformed conductors 25 (12of which in the represented embodiment) not yet subjected to anytwisting. In FIG. 19, the arrow P_I indicates the insertion position ofthe last U-shaped preformed conductor 25.

Returning to FIG. 18, after the filling of the pockets marked by thecircle in FIG. 19, the position of the first 51 and second 52 body isfixed by bringing the two punches 61′, 62′ into advanced position. Atthis point, by moving the rotating table 36, the twisting device 50 isbrought into the station 32 for inserting the special conductors S1, S2,S3. In this station 32, the special conductors 51, S2, S3 are inserted,e.g. manually, into the pockets marked in FIG. 19 by the square. Forexample, the following are inserted: three terminals S1, three jumpersS2 and a neutral conductor S3. Subsequently, the twisting device 50 isbrought into the twisting station 33, in which the punches 61′, 62′ arebrought in moved-back position and in which a first servo motor and asecond servo motor, not shown in the figures, are respectively coupledto the first body 51 and to the second body 52, e.g. by means of pinsinsertable in the respective seats 81 and 82. In accordance with oneembodiment, the two bodies 51, 52 are driven in rotation in oppositedirections by means of associated servo motors. Such driving in rotationis carried out according to a predefined twisting pitch (e.g. equal toeight slots), which shall be called second predefined twisting pitch incontrast to the first predefined twisting pitch mentioned above. In sucha manner, one obtains a first plurality of basic conductors U1 havinglegs spaced from each other by a distance equal to the sum of said firstand second predefined pitch and a second plurality of basic conductorsU2 having legs spaced from each other by said second predefined pitch.

It is also observed that in the specific embodiment described withreference to FIG. 19, after the above-described twisting at the twistingstation 33, it will be possible to obtain a set of bar conductors. Suchbar conductors, after having been extracted from the twisting device 50and inserted in the stator core slots 2, allow making a stator 1comprising:

-   -   a stator core 2 comprising a cylindrical body in which a        circular array of slots 8 is defined, each slot 8 comprising at        least one first P1 and at least one second P2 insertion        position, radially aligned with respect to each other;    -   at least one bar winding comprising a first plurality of basic        conductors U1, U2 having two legs 5 and a connection portion 15        between said legs, the first plurality of basic conductors U1,        U2 comprising at least one first set of conductors U1 having        legs offset from each other by a first pitch and a second set U2        of conductors having legs offset from each other by a second        pitch different from the first pitch; the bar winding also        comprises a second plurality of special bar conductors S1, S2,        S3 for the completion of the winding having one or more legs,        the legs 5 of the conductors of the first and second plurality        belonging to a first or a second circular array of legs, based        on the occupied insertion position. The first and the second        circular array each comprise:    -   a first arc of legs of the first set of conductors U1 delimited        by a respective initial and final leg of said conductors U1 of        the first set;    -   an arc complementary to said first arc in which legs are        inserted of the second set of conductors U2 as well as legs of        the special bar conductors S1, S2, S3.

With reference to FIG. 20, based on the functioning illustrated above ofthe twisting device 20, it is observed that by generalizing suchfunctioning, a method 100 was in practice described for twistingpreformed conductors for bar windings of electric machines, saidconductors comprising a first and a second leg 5 joined together by aconnection portion 15, the method 100 comprising the steps of:

-   -   a) providing 101 (TW-A_Prov”, in FIG. 20) a twisting apparatus        30 comprising a twisting device 50 having at least a first 51        and a second 52 body coaxial with each other and extended around        a twisting axis Zt-Zt, respectively comprising a first and a        second circular array A1, A2 of pockets with center on such        axis; said bodies 51, 52 are relatively rotatable with respect        to each other around the twisting axis in order to assume a        first insertion configuration, in which respective pockets of        the first and second array are radially aligned with each other        in pairs with respect to the twisting axis;    -   b) loading 102 (“LOAD_1”, in FIG. 20) in a subset of said        pockets, a first plurality of said conductors in a manner such        that aligned pockets of the first and second array respectively        receive a first and a second leg 5 of a respective conductor,        the loading step 102 being such to leave a first residual subset        of pockets free;    -   c) driving 103 (“TWIST_1”, in FIG. 20) the first 51 and the        second 52 body in relative rotation around said axis Zt-Zt, in        order to distance such legs 5 from each other by a first        pre-established twisting pitch, until a second insertion        configuration is reached in which a second plurality of pockets        of the first and second body and said residual subset are        radially aligned with respect to each other.

The twisting method 100 also comprises, after the driving in rotationstep 103, the steps of:

-   -   d) loading 104 (“LOAD_2”, in FIG. 20) in a second subset of said        second plurality of pockets, a second plurality of preformed        conductors in a manner such that aligned pockets of the first        and second array belonging to said second subset respectively        receive a first and a second leg 5 of a respective preformed        conductor;    -   e) driving 106 (“TWIST_2”, in FIG. 20) the first and the second        body in relative rotation around said axis Z-Z, in order to        distance the legs 5 of a second plurality of conductors from        each other by a second pre-established twisting pitch and to        further distance the legs of the first plurality of conductors        from each other by said second pre-established twisting pitch,        therefore obtaining said first plurality of conductors having        legs spaced from each other by a distance equal to the sum of        said first and second pitch and said second plurality of        conductors having legs spaced from each other by said second        pitch.

In accordance with one possible embodiment, in the loading step 104, asecond residual subset of pockets is left free, and the method alsocomprises a step 105 for loading (“LOAD_3”, in FIG. 20) pockets of saidsecond residual subset with a plurality of special preformed barconductors S1, S2, S3 intended to complete a winding. In accordance withone embodiment, the step of loading 105 pockets with said secondresidual subset is carried out before executing said driving step 106.

In accordance with a particular embodiment, the aforesaid firstpre-established pitch is equal to the angular distance between thecenters of two adjacent pockets of a same array.

In accordance with a further embodiment, the loading steps 102 and 104are carried out by inserting the legs of the conductors in the pocketsin a fixed insertion position and making said first 51 and said second52 body rotate, maintaining said bodies integral with each other duringrotation. In particular, said rotation can be carried out by driving inrotation only one of said first or second body; the other of said bodiesis locked to the driven body by the first removable locking means 55adapted to prevent a relative rotation between said bodies 51, 52 but toallow a rotation of both bodies with respect to an external reference.

In accordance with one embodiment, the driving step 103 is carried outby driving in rotation one of said first and second bodies 51, 52,maintaining in a fixed angular position the other of said bodies bymeans of second locking elements 61, 62.

In accordance with one embodiment, in the loading step 102 a first arcof said pocket arrays is loaded, leaving free a second arc complementaryto said first arc. In the embodiment described up to now, the first arcis wider than the second arc.

As can be appreciated from that described above, the above-illustratedstator and rotor, twisting method and the apparatus allow meeting therequirements described above with reference to the prior art.

Indeed, it is observed that the aforesaid method allows carrying out, inan automated manner, a twisting with differential pitch; through this,it is possible to make windings for which the bending of the endportions 7 projecting from the welding face 4, after the insertion ofthe bar winding in the slots 8 of a stator core 2, can be carried out ina relatively simple and convenient manner. The same is valid for thewelding of such bent end portions 7.

A man skilled in the art, in order to meet contingent and specificrequirements, can make numerous changes and variations to the method andthe apparatus described above, all contained in the scope of theinvention as defined by the following claims.

The invention claimed is:
 1. Stator or rotor of an electric machine,comprising: a stator core or a rotor core comprising a main cylindricalbody in which a circular array of slots are defined, each slotcomprising at least a first and at least a second insertion position,radially aligned with respect to each other; at least one bar windingcomprising a first plurality of basic conductors having two legs and aconnection portion between said legs, said first plurality of basicconductors comprising at least a first set of conductors having legsoffset from each other by a first pitch and a second set of conductorshaving legs offset from each other by a second pitch different from thefirst pitch, the bar winding also comprising a second plurality ofspecial bar conductors for the completion of the winding having one ormore legs, the legs of the conductors of the first and second pluralitybelonging to a first or a second circular array of legs based on theoccupied insertion position; characterized in that the first and thesecond circular array comprise: a first arc of legs of the first set ofconductors delimited by a respective initial and final leg of saidconductors; a second arc complementary to said first arc in which legsof the second set of conductors, and legs of the special bar conductors,are inserted.
 2. Stator or rotor according to claim 1, wherein one ormore of said conductors are covered on their surface by an insulationlayer of electrically insulating material.
 3. Stator or rotor accordingto claim 2, wherein said insulating material is an insulating enamel. 4.Stator or rotor according to claim 1, wherein one or more saidconductors are made of copper and are flat rectangular conductors,having a pair of opposite faces which are farther away from each otherthan the distance between the two remaining opposite faces.
 5. Stator orrotor according to claim 4, wherein the two bar conductors inside a sameslot are aligned along a respective short side thereof.
 6. Stator orrotor according to claim 1, wherein a slot of the stator core is crossedby at least two of said conductors and in particular by the legsthereof, and houses a sheet, made of insulating material.
 7. Stator orrotor according to claim 1, wherein one or more of said special barconductors comprise terminals, jumpers or a neutral conductor.
 8. Statoror rotor according to claim 1, wherein the basic bar conductors areobtained by spreading the legs of a preformed “U”-shaped or “P”-shapedbar conductor by a pre-established amount or pitch.
 9. Stator or rotoraccording to claim 8, wherein the basic bar conductors of the first setare obtained via twisting of the U-shaped or P-shaped preformedconductor according to a twisting pitch equal to nine slots, while thebasic bar conductors of the second set are obtained via twisting of the“U”-shaped or “P”-shaped preformed conductor according to a twistingpitch equal to eight slots.
 10. Stator or rotor according to claim 1,wherein the first arc is wider than the second arc.
 11. Electric machinecomprising a stator or a rotor according to claim
 1. 12. Electric orhybrid drive vehicle comprising an electric machine according to claim11.